91903 Mercruiser SCREW (1-3/4 IN.)

Start By: a. remove piston cooling jetsb. remove oil pan1. Use tool (A), and turn the engine flywheel to move the connecting rod cap bolts into a position for removal. 2. Remove bolts (1) to remove bearing caps (2) from the crankshaft and connecting rod. Remove the lower half of the bearing from caps (2).3. Push the connecting rods away from the crankshaft, and remove the upper halves of the bearing from the rods. Install rod bearings dry when the clearance checks are made. Put clean engine oil on the rod bearings for final assembly.
Be sure the tabs in the back of the connecting rod bearings are in the tab grooves of the connecting rod and cap.
4. Clean the surfaces where the bearing halves fit. Install bearing halves (3) in the rods and caps (2).The serviceman must be very careful to use Plastigage, tool (B) correctly. The following points must be remembered: ... Make sure that the backs of the bearings and the bores are clean and dry.... Make sure that the bearing locking tabs are properly seated in their slots.... The crankshaft must be free of oil where the Plastigage touches it.... Put a piece of Plastigage on the crown of the bearing half that is in the cap. Do not allow the Plastigage to extend over the edge of the bearing.... Install the bearing cap using the correct torque-turn specifications. Do not use an impact wrench. Be careful not to dislodge the bearing when the cap is installed.... Do not turn the crankshaft with the Plastigage installed.... Carefully remove the cap but do not remove the Plastigage. Measure the width of the Plastigage while it is in the bearing cap or on the crankshaft journal. Do this by using the correct scale on the package. Record the measurements.... Remove the Plastigage before reinstalling the cap.When using Plastigage, the readings can sometimes be unclear. For example, all parts of the Plastigage are not the same width. Measure the major widths to make sure that they are within the specification range. Also, experience has shown that when checking clearances tighter than 0.10 mm (.004") the readings may be low by 0.013 to 0.025 mm (.0005 to .0010"). Out-of-round journals can give faulty readings. Also, journal taper may be indicated when one end of the Plastigage is wider that the other.For complete details concerning measuring bearing clearances, see Engine Bearings And Crankshafts, Form No. SEBD0531. 5. Check the bearing clearance with Plastigage (B). Put caps (2) in position on the connecting rods, and make sure the number on the side of the cap is next to and respective with the number on the side of the connecting rod. Tighten the bolts in the number sequence shown as follows: Bolts (4) and (5) are installed on the same side of the rod cap that has the locating pin. The locating pin must extend 4.0 0.5 mm (.16 .02 in.) from the rod cap.a. Put 2P2506 Thread Lubricant or Fel-Pro C100 Lubricant on the bolt threads and contact surfaces of the bolts and caps.b. Hand tighten bolts No. 4 and No. 5 to a torque of 90 5 N m (65 4 lb.ft.).c. Hand tighten bolts No. 6 and No. 7 to a torque of 90 5 N m (65 4 lb.ft.).d. Hand tighten bolts No. 4 and No. 5 to a torque of 90 5 N m (65 4 lb.ft.).e. Hand tighten bolts No. 6 and No. 7 to a torque of 90 5 N m (65 4 lb.ft.).f. Hand tighten each bolt an additional 90 5°.6. Remove the rod cap, and measure the Plastigage. The rod bearing clearance must be 0.107 to 0.218 mm (.0042 to .0086 in.).7. Put 2P2506 Thread Lubricant or Fel-Pro C100 Lubricant on the bolt threads and contact surfaces of the bolts and caps before final assembly. Put clean engine oil on both halves of the rod bearings. Put caps (2) in position, and tighten the bolts as in Steps 5b through 5e. An impact wrench can be used for the final tighten torque of 90 5° in Step 5f.End By: a. install piston cooling jetsb. install oil pan